// Protocol Buffers - Google's data interchange format
// Copyright 2008 Google Inc.  All rights reserved.
// https://developers.google.com/protocol-buffers/
//
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions are
// met:
//
//     * Redistributions of source code must retain the above copyright
// notice, this list of conditions and the following disclaimer.
//     * Redistributions in binary form must reproduce the above
// copyright notice, this list of conditions and the following disclaimer
// in the documentation and/or other materials provided with the
// distribution.
//     * Neither the name of Google Inc. nor the names of its
// contributors may be used to endorse or promote products derived from
// this software without specific prior written permission.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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package com.google.protobuf;

import com.google.protobuf.Internal.ProtobufList;

import java.util.ArrayList;
import java.util.Collections;
import java.util.List;

/**
 * Utility class that aids in properly manipulating list fields for either the lite or full runtime.
 */
abstract class ListFieldSchema {
    // Disallow construction.
    private ListFieldSchema() {
    }

    private static final ListFieldSchema FULL_INSTANCE = new ListFieldSchemaFull();
    private static final ListFieldSchema LITE_INSTANCE = new ListFieldSchemaLite();

    abstract <L> List<L> mutableListAt(Object msg, long offset);

    abstract void makeImmutableListAt(Object msg, long offset);

    abstract <L> void mergeListsAt(Object msg, Object otherMsg, long offset);

    static ListFieldSchema full() {
        return FULL_INSTANCE;
    }

    static ListFieldSchema lite() {
        return LITE_INSTANCE;
    }

    /**
     * Implementation for the full runtime.
     */
    private static final class ListFieldSchemaFull extends ListFieldSchema {

        private static final Class<?> UNMODIFIABLE_LIST_CLASS =
                Collections.unmodifiableList(Collections.emptyList()).getClass();

        @Override
        <L> List<L> mutableListAt(Object message, long offset) {
            return mutableListAt(message, offset, AbstractProtobufList.DEFAULT_CAPACITY);
        }

        @Override
        void makeImmutableListAt(Object message, long offset) {
            List<?> list = (List<?>) UnsafeUtil.getObject(message, offset);
            Object immutable = null;
            if (list instanceof LazyStringList) {
                immutable = ((LazyStringList) list).getUnmodifiableView();
            } else if (UNMODIFIABLE_LIST_CLASS.isAssignableFrom(list.getClass())) {
                // already immutable
                return;
            } else if (list instanceof PrimitiveNonBoxingCollection && list instanceof ProtobufList) {
                if (((ProtobufList<?>) list).isModifiable()) {
                    ((ProtobufList<?>) list).makeImmutable();
                }
                return;
            } else {
                immutable = Collections.unmodifiableList((List<?>) list);
            }
            UnsafeUtil.putObject(message, offset, immutable);
        }

        @SuppressWarnings("unchecked")
        private static <L> List<L> mutableListAt(Object message, long offset, int additionalCapacity) {
            List<L> list = getList(message, offset);
            if (list.isEmpty()) {
                if (list instanceof LazyStringList) {
                    list = (List<L>) new LazyStringArrayList(additionalCapacity);
                } else if (list instanceof PrimitiveNonBoxingCollection && list instanceof ProtobufList) {
                    list = ((ProtobufList<L>) list).mutableCopyWithCapacity(additionalCapacity);
                } else {
                    list = new ArrayList<L>(additionalCapacity);
                }
                UnsafeUtil.putObject(message, offset, list);
            } else if (UNMODIFIABLE_LIST_CLASS.isAssignableFrom(list.getClass())) {
                ArrayList<L> newList = new ArrayList<L>(list.size() + additionalCapacity);
                newList.addAll(list);
                list = newList;
                UnsafeUtil.putObject(message, offset, list);
            } else if (list instanceof UnmodifiableLazyStringList) {
                LazyStringArrayList newList = new LazyStringArrayList(list.size() + additionalCapacity);
                newList.addAll((UnmodifiableLazyStringList) list);
                list = (List<L>) newList;
                UnsafeUtil.putObject(message, offset, list);
            } else if (list instanceof PrimitiveNonBoxingCollection
                    && list instanceof ProtobufList
                    && !((ProtobufList<L>) list).isModifiable()) {
                list = ((ProtobufList<L>) list).mutableCopyWithCapacity(list.size() + additionalCapacity);
                UnsafeUtil.putObject(message, offset, list);
            }
            return list;
        }

        @Override
        <E> void mergeListsAt(Object msg, Object otherMsg, long offset) {
            List<E> other = getList(otherMsg, offset);
            List<E> mine = mutableListAt(msg, offset, other.size());

            int size = mine.size();
            int otherSize = other.size();
            if (size > 0 && otherSize > 0) {
                mine.addAll(other);
            }

            List<E> merged = size > 0 ? mine : other;
            UnsafeUtil.putObject(msg, offset, merged);
        }

        @SuppressWarnings("unchecked")
        static <E> List<E> getList(Object message, long offset) {
            return (List<E>) UnsafeUtil.getObject(message, offset);
        }
    }

    /**
     * Implementation for the lite runtime.
     */
    private static final class ListFieldSchemaLite extends ListFieldSchema {

        @Override
        <L> List<L> mutableListAt(Object message, long offset) {
            ProtobufList<L> list = getProtobufList(message, offset);
            if (!list.isModifiable()) {
                int size = list.size();
                list =
                        list.mutableCopyWithCapacity(
                                size == 0 ? AbstractProtobufList.DEFAULT_CAPACITY : size * 2);
                UnsafeUtil.putObject(message, offset, list);
            }
            return list;
        }

        @Override
        void makeImmutableListAt(Object message, long offset) {
            ProtobufList<?> list = getProtobufList(message, offset);
            list.makeImmutable();
        }

        @Override
        <E> void mergeListsAt(Object msg, Object otherMsg, long offset) {
            ProtobufList<E> mine = getProtobufList(msg, offset);
            ProtobufList<E> other = getProtobufList(otherMsg, offset);

            int size = mine.size();
            int otherSize = other.size();
            if (size > 0 && otherSize > 0) {
                if (!mine.isModifiable()) {
                    mine = mine.mutableCopyWithCapacity(size + otherSize);
                }
                mine.addAll(other);
            }

            ProtobufList<E> merged = size > 0 ? mine : other;
            UnsafeUtil.putObject(msg, offset, merged);
        }

        @SuppressWarnings("unchecked")
        static <E> ProtobufList<E> getProtobufList(Object message, long offset) {
            return (ProtobufList<E>) UnsafeUtil.getObject(message, offset);
        }
    }
}
